The present invention relates to phenolic resin compositions which are curable in the presence of a vaporous tertiary amine catalyst at room temperature and more particularly to stabilizing such resins for improved pot lives thereof.
Vapor permeation cure is a method for curing specialized coatings by exposure of such surface coatings to a vaporous tertiary amine catalyst. Such curing is performed at room temperature and requires less than a minute of vaporous catalyst exposure to achieve tack-free coatings. Several prior patents show coating compositions composed of a polyhydroxy polyester and a polyisocyanate which can be vapor permeation cured. The polyhydroxy polyester often is an aromaic hydroxyl-containing polyester as aromatic hydroxyl groups are most suitable for vapor permeation curing.
One exemplary composition especially adapted for vapor permeation curing as a surface coating is found in commonly assigned British Patent No. 1,351,881. The phenol-functional polyester resin of this prior teaching is a linear polyester which has each chain end-capped with a polyether phenolic resin, such as preferably shown in U.S. Pat. No. 3,485,797. Such polyether phenolic resin is characterized by containing a large proportion of benzylic ether linkages in the ortho position relative to the phenol group. The polyether phenol resin is reacted onto both ends of the linear polyester chain to provide terminal phenol groups which react with a multi-isocyanate agent when exposed to a vaporous tertiary amine catalyst according to this British patent.
Unexpectedly, the present invention is based upon the discovery that a plurality of residual methylol groups of such polyether phenol-capped resins undesirably substantially diminish the pot life of the coating composition. The solution to such diminished pot life without significant sacrifice of ultimate coating properties is the achievement of the present invention.